Ethylene, the smallest plant hormone, plays a role in many developmental processes in plants. It initiates the ripening of fruit, promotes seed germination and flowering, and is responsible for the senescence of leaves and flowers. As fruits and vegetables start ripening, ethylene is produced and emitted, and the internal ethylene concentration in some fruits is used as a maturity index to determine the time of harvest. In some vegetables and fruits, such as bananas, exposure to ethylene gas results in a continuation of the ripening process after harvesting, thus the monitoring of ethylene gas in storage rooms is important to avoid the deterioration of ethylene sensitive produce.